PSN-L Email List Message

Subject: Re: Modified sound card and datalogging and geophones
From: Gordon Couger gcouger@..........
Date: Thu, 21 Jul 2005 17:39:27 -0500

Doug Crice wrote:
> I am using standard seismic sensors and I will probably use a .22 or .38
> fired into the ground or a slide hammer lifted up by a blank cartridge. My
> sledge hammer swinging days have been over for 20 years due to multiple
> sclerosis.
> Shooting bullets into the ground is not the best energy source; most of the
> energy goes into plastic deformation instead of elastic waves.  There was a
> source made with an 8-gague kiln gun some years ago that generated a lot of
> sound and fury, but barely kept up with a sledgehammer except when fired
> into saturated material. 
> The best gun-like source is the buffalo gun aka "in hole shotgun".  You take
> a 3/4-inch pipe about 4 feet long and screw a coupling on the end big enough
> to hold a shotgun shell.  You auger a hole in the ground and stick the end
> with the shell down a foot or more.  Then you drop a pointed rod down the
> pipe to detonate the shell.  The shell goes off underground and much more of
> the energy is coupled to the soil.  It works about as well with blanks as
> with loaded shells. Search for in-hole shotgun source on the web and you
> will find some papers. The most descriptive here
> 00052000007000985000001&idtype=cvips&gifs=yes
> There is a commercial version called the Betsy Seisgun, if you search there
> you can see pictures of it, but the pipe version works just as well. 
> Doug Crice
> Wireless Seismic  
> 12996 Somerset Drive                phone 1-530-274-4445
> Grass Valley,  CA  95945  USA    fax 1-530-274-4446


I know a gun fired in the ground is not a good source and that's 
why I included a drop hammer lifted by a bank and dropped back 
on the rod that is attached to a steel plate that sets on the 
ground. I may have to use a propane to lift the slide over the 
piston instead of a blank shot gun shell,

This fall when it cools off I will see what kind of hammer I need.



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